1. Field of the Invention
The present invention relates to wireless communications and in particular to a method and apparatus of traffic offloading in a network.
2. Discussion of the Related Art
Recently, a machine-to-machine (M2M) system may be considered, which system comes into the spotlight as the next generation communication technology and is enacted as a new standard so as to also support in the IEEE 802.11 WLAN. The M2M system means a network to transmit and receive information in which a communication subject as machines rather than people. Large machines such as process machinery in a plant, automobiles and the like may be also elements of the M2M system including the home appliances such as temperature or humidity sensors, a camera, a TV and the like. Recently, according to the introduction of a variety of communication services such as smart grids, e-Health, and ubiquitous services, the M2M technologies are utilized to support the services. The characteristics of the M2M system are as follows:
1) A large number of stations: It is assumed that the M2M terminal includes a large number of stations unlike the existing network. This is because all sensors installed at home, company, etc. may be considered as well as machines owned by individuals. Thus, the large number of stations may be connected to one AP.
2) A low traffic load for each station: The M2M terminal is not required to transmit information frequently and the amount of information is less since it has traffic patterns that collects and reports the surrounding information.
3) Uplink center: The M2M terminal has a structure that receives commands by mainly downlink and then reports the resulted data by uplink. Since the main data is usually transmitted by the uplink, the uplink is centered in the M2M terminal.
4) Long life of Station: The M2M terminal is mostly battery-operated, and it is often difficult to charge the battery frequently by users. Thus, the M2M terminal is required to ensure a long life by minimizing battery consumption.
5) Auto-recovery function: The M2M terminal is required to have an auto-recovery function since they are difficult to directly manipulate the terminal in a particular situation.
The IEEE 802.11ah standard is being discussed as one use case of such a M2M communication. The main feature of the standard is that the unlicensed band of sub-1 GHz, except for the TV white space band, has much wider coverage (up to 1 km) than that of the WLAN in the center of the existing indoor. That is, when the WLAN is used in the sub 1 GHz band represented as 700-900 MHz different from the existing 2.4 GHz or 5 GHz, the coverage of the AP is extended about 2-3 times due to propagation characteristics of the corresponding band, compared to the same transmission power. This case has a feature in that the large number of STAs may be connected to one AP. The use case considered in the IEEE 802.11ah standard can be summarized as follows:
Use Case 1: Sensors and meters
1a: Smart Grid—Meter to Pole
1c: Environmental/Agricultural Monitoring
1d: Industrial process sensors
1e: Healthcare
1f: Healthcare
1g: Home/Building Automation
1h: Home sensors
Use Case 2: Backhaul Sensor and meter data
Backhaul aggregation of sensors
Backhaul aggregation of industrial sensors
Use Case 3: Extended range Wi-Fi
Outdoor extended range hotspot
Outdoor Wi-Fi for cellular traffic offloading
In the Use Case 1, which is the use case on the M2M communication using sensors and meters as described above, the various types of sensor devices can be connected to the 802.11ah AP to perform the M2M communication. In particular, in a case of the smart grid, the maximum 6,000 sensor devices may be connected to one AP.
In the Use Case 2, which is a case of the backhaul sensor and meter data, the 802.11ah AP that provides a wider coverage would serve as the backhaul link of other system such as the 802.15.4 g.
In the Use Case 3, it may be the use case aimed for outdoor extended range hotspot communication such as an extended home coverage, a campus wide coverage, shopping malls and the case aimed for distribution of the overflowing cellular traffic by which the 802.11ah AP supports traffic offloading of the cellular mobile communication.